Pothead for electric cable



Oct. 4, 1955 E. F. CRONIN POTHEAD FOR ELECTRIC CABLE Filed Sept. 1, 1954 [7/527/51 Edward F (rap/'27, 15%; f m [275 flffrflgy- POTHEAD FOR ELECTRIC CABLE Edward F. Cronin, Lenox, Mass., assignor to General Electric Company, a corporation of New York Application September 1, 1954, Serial No. 453,570

Claims. (Cl. 174-75) This invention relates to terminations for electric cables, and more particularly to an improved pothead for high voltage electric power cables.

In customary pothead construction, an insulator and a wiping sleeve are individually attached to a common mounting flange from which they extend in opposite directions. Such construction requires maintaining close dimensional tolerances of the parts in order to obtain a good fit and satisfactory seals between the parts.

In accordance with this invention, the wiping sleeve extends through the mounting flange to which it is permanently attached, and by means of mating beveled or tapered surfaces on the parts, they can be made with relatively wide dimensional tolerances while still maintaining a good fit and tight seal between the parts. One end of the insulator fits into one end of the wiping sleeve at the mounting flange so that only one seal is necessary, and the insulator and wiping sleeve are fastened directly together. This results in an extremely simple, durable and inexpensive construction.

An object of the invention is to provide a new and improved pothead construction.

Another object of the invention is to provide a novel pothead construction which is simple, durable and of low cost.

The invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring now to the single figure of the accompanying drawing, this shows a longitudinal sectional view of a preferred embodiment of the invention applied to an electric cable having a central stranded conductor 1, surrounded by suitable insulation 2, and covered by a protective sheath 3, typically made of lead.

The principal parts of the pothead are a mounting flange 4, a wiping sleeve 5, an insulator 6, and a terminal assembly 7.

The mounting flange, which may be constructed of brass plate, is preferably provided with a plurality of peripheral mounting holes 8 and a central opening having beveled or tapered walls 9. The wiping sleeve 5, which may be spun from sheet copper, has an intermediate section of frusto-conical shape which is seated in the central opening of the mounting flange 4 so that the beveled or tapered surfaces of the wall 9 and the intermediate section 10 are in engagement with each other throughout the thickness of the mounting flange 4. The mounting flange 4 and the wiping sleeve 5 are permanently attached to each other in any suitable manner such as by brazing, as indicated at 11. The exact diameter of the central opening in the mounting flange 4, and the exact diameter of the intermediate section 10 of the wiping sleeve 5 are not critical because their tapered shape will permit close fitting or mating of their surfaces by slight axial displacement or adjustment of the parts before they are brazed together.

The insulator 6, which may be constructed of any United States Patent 0 M 2,719,875 Patented Oct. 4, 1955 suitable insulating material preferably glazed porcelain or glass, is provided at one end with a taper 12 on its outer surface, the smaller diameter of which is at the extreme end of the insulator and the larger diameter of which terminates in a shoulder 13. This tapered or frusto-conical end surface of the insulator is seated in the intermediate section 10 of the wiping sleeve and preferably a resilient sealing gasket 14 is interposed between the mating surfaces of those parts. Here again the diameter of the tapered or beveled end of the insulator is not critical and slight variations in the diameter will merely mean a slight axial displacement of the insulator 6 with respect to the mounting flange 4.

The insulator 6 is fastened directly to the wiping sleeve 5 in any suitable manner, preferably by spinning the end 15 of the wiping sleeve over the shoulder 13 of the insulator after the parts have been forced together in a suitable jig during manufacture so as to secure the desired tight fit and compression of the resilient sealing gasket 14.

It will be observed that radially outward pressure exerted on the relatively thin walls of the wiping sleeve 5 when the insulator 6 is forced into the intermediate section 10 in compressing the gasket 14 is opposed by the relatively thick and solid mounting flange 4, so that substantial pressure can be applied without distorting or bending the intermediate section 10 of the wiping sleeve.

The terminal assembly in the other end of the insulator 6 comprises a metal bushing 16 of low resistance material such as copper having an integral shoulder or flange 17, and an intermediate threaded portion 18 cooperating with a clamping nut 19. Interposed between the shoulder 17 and the insulator is a split resilient cushion 20, and interposed between the nut 19 and the outer top surface of the insulator 6 is a resilient sealing gasket 21. An opening 22 is provided in the outer end of the terminal bushing 16 through which molten solder can be poured for permanently attaching the bushing 16 to the stranded copper conductor 1 which is inserted therein.

The end of the wiping sleeve 5 remote from the mounting flange 4 has a reduced diameter section 23 which may be sealed to the sheath 3 of the cable with which the pothead is used in any suitable manner such as by wiped solder joint 24.

The wiping sleeve 5 is preferably provided with a side opening 25 over which an internally threaded thimble or boss 26 is brazed or soldered to the wiping sleeve. A threaded fill and drain plug 27 is inserted in the member 26.

In the installation of the pothead when it is desired to fill it with insulating liquid such as mineral oil, the clamping nut 18 may be loosened so that when fluid is injected into the pothead through the opening 25 air can escape through the slit (not shown) in the resilient cushion 20. After the pothead has been filled with fluid the nut 19 can be drawn down tight so as to compress the sealing gasket 21 and seal the top end of the pothead.

While there has been shown a particular embodiment of the invention, it will be obvious to those skilled in the art that changes can be made without departing from the invention, and therefore it is aimed in the appended claims to cover all such changes and modifications as fall within the true scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A pothead for an electric power cable comprising in combination, a mounting flange having a central opening with tapered side walls, a wiping sleeve having a frusto-conical intermediate section seated in said opening against said tapered side walls, means for fastening said mounting flange and wiping sleeve together, an elongated hollow insulator having a frusto-conical outer end surface whose minimum diameter is at the end of said insulator, said frusto-conical insulator end surface being seated in the frusto-conical section of said wiping sleeve opposite the tapered walls of the opening in said mounting flange, means for fastening the end of said wiping sleeve adjacent said mounting flange to said insulator, and a terminal member in the other end of said insulator for attachment to the conductor of an insulated electric power cable which is inserted in said pothead through said wiping sleeve.

2. A pothead for an electric power cable comprising, in combination, a mounting flange having a central opening with tapered side walls, a wiping sleeve having a frusto-conical intermediate section seated in said opening against said tapered side walls, means for fastening said flange and sleeve together, an elongated hollow insulator having a frusto-conical outer end surface whose minimum diameter is at the end of said insulator and whose maximum diameter terminates in a shoulder, said frusto-conical insulator end surface being seated in the frusto-conical section of said wiping sleeve opposite the tapered walls of the opening in said mounting flange whereby said wiping sleeve and insulator extend in opposite directions from said mounting flange, the end of said wiping sleeve adjacent said insulator being curved inwardly over said shoulder so as to clamp the frustoconical end of said insulator in the frusto-conical section of said wiping sleeve where the opposite side of said section is in contact with the tapered walls of the opening in said mounting flange, and a terminal member in the other end of said insulator for receiving the conductor of an insulated electric power cable which is inserted in said pothead through said wiping sleeve.

3. A pothead as in claim 2 having a resilient sealing gasket between the mating frusto-conieal surfaces of the wiping sleeve and insulator.

4, A pothead for an insulated electric power cable comprising, in combination, a brass plate mounting flange having a plurality of peripheral mounting holes and a beveled central opening, a sheet copper wiping sleeve having a flared intermediate section seated in said beveled opening with the beveled and flared surfaces in mating contact with each other throughout the thickness of said flange, said flange and sleeve being brazed together, a hollow generally cylindrical insulator having a tapered outer end surface which matches the surface of the flared section of said wiping sleeve seated in said flared section of said wiping sleeve, a shoulder on said insulator, the end of said wiping sleeve adjacent said insulator being curved inwardly over said shoulder so as to clamp said insulator to said wiping sleeve, and a conductive terminal member in the other end of said insulator for receiving an end of a cable conductor.

5. A pothead as in claim 4 having a resilient sealing gasket between the mating surfaces of the wiping sleeve and insulator.

Steinmayer Oct. 13, 1936 Gutzma'n'n et al Sept. 29, 1942 

